The invention concerns an electric clock driven by solar energy and having a 400-day torsion pendulum. A clock of this generic type is known from German Publication GM- No. 78 24 116.
This invention recognizes that the traditional value of such a 400-day clock is the result of the minimum amount of manual manipulations required for its operation. The torsion pendulum drive is protected under a glass hood, and the clock mechanism exhibits an exceedingly long operating period based on a mechanical energy accumulator. Even after the advent of electronic timekeeping which rendered torsion pendulums obsolete, they were retained for esthetic reasons and maintained in motion by the electrical energy source, occasionally even by the geared or electromechanical drive of the clockworks itself. Despite the advanced electromechanical drive of the clockworks, permanent operation still requires certain manual actuations, e.g., replacement of the electrochemical battery, which is overlaid by the solar cell having a relatively small surface area and being hidden behind the dial face shield.
It is an object of the invention to enhance the usefulness of a timepiece of the afore-mentioned generic type by further reducing the need for the removal of the glass hood of a 400-day clock and possibly even eliminating it in permanent operation.